1. Field of the Invention
The present invention relates to a position sensing assembly for determining the rotating position of such engine parts as camshafts or crankshafts.
2. Disclosure Information
Electronic engine control systems have been in widespread use for a number of years in the automotive industry. The control of fuel injection and spark timing require precise information regarding the position of the engine's internal parts i.e. crankshaft, pistons, valves, etc. as the engine progresses through the usual 2 or 4-stroke cycles. The need for precise information as to the location of a camshaft is increasingly underscored by the use of such devices as variable camshaft timing. This has in turn necessitated the use of camshaft position sensors. A problem with automotive engines arises because packaging considerations do not always allow for a sensor to be mounted on the front of the engine, for example, to promote easy accessibility for service. Mounting of a camshaft sensor through a camshaft cover, as illustrated in FIG. 1, is a known attempt to provide a solution to the packaging problem.
The sensor shown at 10 in FIG. 1 is mounted and retained through camshaft cover 16 and retained within the cover by means of bolt 12. The sensor is mounted within aperture 14 formed in cam cover 16. Accurate operation of sensor 10 requires that the air gap between sensor 10 and the teeth contained on wheel 18, which is mounted to a camshaft, be accurately maintained at relatively small distance of 0.5–2.0 mm. Unfortunately, tolerance stack-up in the cam cover system, including cover 16 and any associated gasketing will impair the ability to accurately measure the position of the camshaft. This occurs because tolerance growth or other tolerance uncertainty will cause the position of sensor 10 with respect to wheel 18 to be unpredictable, and as a result the output of sensor 10 will not be reliable over long engine production runs.
The present invention solves the difficulties engendered by prior art position sensing systems, while providing a mounting system which requires only that the sensor be snapped into place by the production operator. This allows quick, error-free mounting of the sensor, while at the same time providing a seal which simultaneously prevents fluid from escaping from the engine, while preventing dirt from ingressing into the engine.